A British resident has been blinded in one eye by American military police at Guantanamo Bay, his lawyer claimed today.

Omar Deghayes' family appealed for the British Government to intervene and secure his release, almost 25 years to the day since his father was assassinated by Colonel Gaddafi's regime in Libya.

Mr Deghayes mother Zohra Zewawi, from Brighton, wept as lawyer Clive Stafford Smith described the injuries the detainee has allegedly suffered at the Cuban base.

"In March 2004 the Emergency Reaction Force in Camp Delta came into his cell," he said.

"They brought their pepper spray and held him down.

"They held both of his eyes open and sprayed it into his eyes and later took a towel soaked in pepper spray and rubbed it in his eyes.

"Omar could not see from either eye for two weeks but he gradually got sight back in one eye.

"He's totally blind in the right eye. I can report that his right eye is all white and milky - he can't see out of it because he has been blinded by the US in Guantanamo."

Mr Stafford Smith added that one of the officers also pushed his finger into Mr Deghayes' eye.

It was a combination of the pepper spray and the gouging which led to loss of his sight, the lawyer claimed.

Mr Deghayes, 35, came to the UK with his family from Libya in 1986, six years after his father, Amer, was allegedly killed by the Gaddafi regime - an incident reported by Amnesty International at the time.

The detainees' brother Taher Deghayes, 38, and sister Amani Deghayes, 30, joined their mother in asking Foreign Secretary Jack Straw to step up diplomatic efforts to secure either his fair trial or release.

Amani, who is legally qualified but is currently a full time mother, added: "Omar has always been someone who cares about justice, he is a fair person and he has always been very well meaning.

"I don't ever believe he would do something like a terrorist attack on civilians or anyone else.

"I can't believe you can hold someone for three years in such terrible conditions without coming up with evidence."

She said it was "laughable" that the Libyan government - from which the family fled 25 years ago - is seen to have diplomatic responsibility for her brother and that Britain - which gave them refuge from persecution - has so far refused to intervene.

Mr Deghayes was a law student and has been held at the military base since early 2002. He is a British resident and had applied for British citizenship.

The detainee travelled from the UK to Afghanistan, where he met and married an Afghan woman and they have a four-year-old son, Suleiman.

Material based on Mr Stafford Smith's conversations with his client were declassified by the US last Friday.

The lawyer's statement describes other incidents in which Mr Deghayes was abused in Guantanamo.

In one case another prisoner's faeces was smeared on Mr Deghayes' face by one of the officers.

Mr Stafford Smith said his client had also had his head pushed in the toilet by US guards, in a separate incident he was kneed in the nose and slammed face down on the concrete surface of a recreation yard.

The detainee studied law at Wolverhampton University and began his Legal Practice Course at Huddersfield University in 1998, but had yet to complete it when he went to Afghanistan.

"He wanted to go to Afghanistan for the simple reason that he is a Muslim and he wanted to see what it was like," said Mr Stafford Smith